Double extendible or support ladder

Abstract

A step ladder with rungs which can be retracted and transformed, without dismantling, into a folded ladder and an extension ladder.

I claim: 
     
       1. A double ladder with rungs which can be folded away-retracted and transformed, without dismantling, into a support ladder or a flat extendible ladder characterised in that each part (1,5) is formed by two straight uprights (2,3 and 6,7) having an identical section (9) in the general shape of a straight open U/channel bar, facing one another and between which identical rungs (4,8) are fixed by a pivoting axis (38); these rungs have a section (16) in the general shape of an open U/channel bar, with dimensions which are less than the section of the uprights; at least one of the parts comprises a device (34) for holding the ladder open, a fixed device which is placed below a rung (4,8) when the ladder is closed; section (9) of the uprights comprising, on the lateral side forming the base, a guide groove (13) in the general shape of a T and into which is slipped, in the two uprights of one part of the ladder, the head (21) of a flat interlocking piece (20), in the general shape of a T, of the two parts (1,5) of the ladder; the interlocking piece (20) is fixed in a limited pivoting position close to the upper end of the two other uprights of the other part of the ladder so that one of the two parts of the ladder may be simultaneously slid parallel to the other and/or pivoted with respect to the other; uprights of one part of the ladder into which are fixed, parallel to the central part, at least one plate (29) termintating in a nose section (29a) in the shape of a hook, emerging from these uprights, a hook part which is placed in a series of slots (31) provided at various eye-level heights in the uprights of the other part of the uprights of the ladder, hooks for holding one part of the ladder with respect to the other when it is being used as a flat extendible ladder. 
     
     
       2. A double ladder in accordance with claim 1, characterized in that its uprights are extended metal sections (9) identical to one another in the shape of a straight U/channel bar, of which the external face (10a) of the central part is straight and forms the external face of each upright; one of the external lateral sides (11) is straight and forms the free side of the uprights and the other side (12) which serves as a base is equipped with the guide groove (13) with the general shape of a T; sections which comprise internally two supporting wings (14,15) parallel to the central part (10); and that its rungs (4, 8) are extruded metallic sections identical to one another in the shape of an open U/channel bar, of which at least one external face 17a of the central part (17) is convex and contains adhesion grooves, whilst the lateral parts (18, 19) are straight. 
     
     
       3. Double ladder in accordance with claim 2, characterized in that the interlocking piece (20) is an elongated piece, which is flat with the exception of its head (21), in the shape of a T, of a size corresponding with the guide groove (13) of the uprights of one part of the ladder into which the head is slid; an interlocking piece which comprises an opening (22) for the passage of a pivoting axis (27) which screws it down in the uprights of the other part of the ladder; a piece which is cut on a face to present three support faces (23, 24, 25) limiting its pivoting, so that, when it is inserted through a slot (28) of sufficient length, provided in the groove (13) of the upright of this second part of the ladder, the interlocking piece rests by one support face (24) or by the other two (23, 25) support faces in these uprights. 
     
     
       4. Double ladder in accordance with claim 3, characterized in that the plates (29) terminating in a nose piece (29a), in the shape of a hook, comprise a straight notch (29b) turned downwards, the width of which is slightly greater than the side of a section (9) used as an upright; and that these plates are fixed by passing through a slot (30) provided along the bottom of the guide groove (13) of the uprights of the part of the ladder into which is slid the head of the interlocking piece; and that the nose piece (29a), in the shape of a hook, emerging from this part of the ladder may be set into a certain number of slots (31) provided at specific distances along the bottom of the guide groove (13) of the uprights of the other part of the ladder; the height of these slots is sufficient to allow the nose of these plates first of all to be raised and then to be taken out. 
     
     
       5. Double ladder in accordance with claim 1, characterized in that the two uprights (6, 7) of the part (5) of the double ladder in which interlocking pieces (20) are fixed, in a free pivoting position, comprise lower separable upright lengths (6a, 7a) obtained by separating horizontally the lengths outside the uprights below the last rung (8); the ends opposite the two parts of the uprights are partially cut in a bevelled fashion to present a partially sloping face; the two parts of the uprights being linked by section lengths (41, 41a) in the shape of an asymmetrical portico, of which the central part (42) rests and is fixed in the upright parts against the internal central face (40), and the two perpendicular wings (43, 44) provided asymmetrically in relation to the central part (42) so that, two sections are reversed in relation to one another, the wings of one are situated on another plane parallel to that of the wings of the other so that, these section lengths being equally cut in a bevelled fashion like the uprights, with the exception of a part of their wings which is extended, these wings face one another so as to allow the insertion of a pivoting axis (45). 
     
     
       6. Double ladder in accordance with claim 5, characterized in that the lengths of the lower uprights (6a, 7a), which are separable, are clamped in a separated position or in a position with the uprights extended, by a ball clamp equipped with a pressure spring which can place itself partially in a first cavity (46) and a second cavity (47) successively of a section wing in the shape of a portico. 
     
     
       7. Double ladder in accordance with claim 5, characterized in that the lengths of the separable lower uprights (6a, 7a) are clamped in a separated position or in a position with the uprights extended, by a sector comprising a curved spring sheet which can place itself partially in a first cavity (46) and a second cavity (47) successively of a section wing in the shape of a portico. 
     
     
       8. Double ladder in accordance with claim 1, characterized in that a plate (34) is provided for holding the ladder open comprises a fixed device placed under a rung (4,8) when the ladder is closed and consists of a plate held in a free pivoting position below a rung of the part of the ladder to which the interlocking pieces (20) are fixed, the rung being at a height which is easily reached by hand; a plate which comprises a slit (34a) forming a holding notch and terminates in a pointed, triangular part (34b): the purpose of this holding notch (34a) is to clamp the plate on a fixed axis (36) when the ladder is open; this fixed axis (36) is held by the lateral sides of an upright, the length of the plate being such that is triangular part (34b) has to be on the other side of the fixed axis (36) even when the ladder is closed, so as to force the end of the plate to pass through an opening (37) provided to the central part (10) of an upright when the ladder is open; this part emerges from the upright and can be lifted in order to release the holding notch of the plate from the fixed axis so as to be able to close the ladder again. 
     
     
       9. Double ladder in accordance with claim 8, characterized in that said plate (34) is held on one side by the fixed axis (36) and when the ladder is closed, on the other side, by the pivoting axis (38) of the upright of the rung (4,8) surmounting the one to which the plate is fixed. 
     
     
       10. Double ladder in accordance with claim 1 characterized in that said uprights are provided with terminal feet (48), rubber components with a convex curve towards the bottom (48a) and adhesion lines surmounted first of all by a part with the general internal dimensions of the section used for the uprights, then by a part (48b) with the general internal dimensions of this same section; a part by which the terminals are fixed by means of an axis (49) to these sections (9), a terminal part (48b) limited to the part on this side of the wings (14, 15) of this section (9). 
     
     
       11. Double ladder in accordance with claim 1, to characterized in that terminal feet (50) are provided on the separable upright lengths (6a, 7a) and have a double bearing (50a, 50b) towards the bottom, also being partially cut in a bevelled fashion in the same way as these lengths. 
     
     
       12. Double ladder in accordance with claim 11 characterized in that the terminal feet (50) are provided with a tongue (50d) placed behind the wings (14, 15) of the section (9) used for the uprights. 
     
     
       13. Double ladder in accordance with claim 12, characterized in that, in a closed position, it takes on the form of a simple chest without any protrusions.